Moderate Resolution Imaging Spectroradiometer (MODIS) is a sensor carried on NASA's Terra and Aqua satellites that identifies areas on the ground that are distinctly hotter than their surroundings and flags them as active fires. The thermal band of MODIS has a 1,000 meter resolution per pixel, so each detection represents roughly a one kilometer area rather than a precise point. Its wide swath means Terra MODIS can image the entire continental US daily in three consecutive orbits, and detections are distributed in near real time through NASA's Fire Information for Resource Management System (FIRMS).
MODIS is older than Visible Infrared Imaging Radiometer Suite (VIIRS), and its coarser resolution can miss smaller or cooler fires that higher-resolution sensors pick up.